umn of water six feet in diameter to the height of 200 feet, while the steam ascends 1,000 feet or more. The eruption is repeated every thirty-two hours, and lasts twenty minutes. In a state of quiescence the temperature of the water at the surface is about 150°.
2. The "Giantess" throws up a large column twenty feet in diameter to a height of sixty feet, and through this great mass it shoots up five or six lesser jets to a height of 250 feet. It erupts about once in every eleven hours, and plays twenty minutes.
3. The "Giant" (Fig. 4) throws a column five feet in diameter 140 feet high, and plays continuously for three hours.
4. The "Beehive" (Fig. 5), so called from the shape of its mound, shoots up a splendid column two or three feet in diameter to the height by measurement of 219 feet, and plays fifteen minutes.
5. "Old Faithful," so called from the frequency and regularity of its eruptions, throws up a column six feet in diameter to the height of 100 to 150 feet regularly every hour, and plays each time fifteen minutes.
Fig. 6.—Forms of Geyser-Craters (after Hayden).
The water of geysers is not volcanic water, but simple spring-water. A geyser is not, therefore, a volcano ejecting water, but a true spring. There has been much speculation concerning the cause of their truly wonderful eruptions.
According to Mackenzie, the eruptions of the Great Geyser may be accounted for by supposing its pipe connected by a narrow conduit with the lower part of a subterranean cave, whose walls are heated by the near vicinity of volcanic fires. Fig. 7 represents a section through the basin, tube, and supposed cave. Now, if meteoric water should run into the cave through fissures more rapidly than it can
